Net-SNMP loads MIBs from two locations by default :
$HOME/.snmp/mibs
/usr/local/share/snmp/mibs
Adding/Copying the F5 MIBs into either of these locations will allow you to perform reverse translations and obtain the OID from the SNMP node name
The F5-BIGIP-SYSTEM-MIB can be found in /usr/share/snmp/mibs/ on an F5 device or online (http://www.oidview.com/mibs/3375/F5-BIGIP-SYSTEM-MIB.html)
snmptranslate -m +F5-BIGIP-SYSTEM-MIB -IR -On sysGlobalHostMemTotal
The -m flag tell snmptranslate to load that MIB in addition to the system defaults, (the leading '+' plus means "also")
The -IR flags tell snmptranslate to do random access to OID labels for input parsing
The -On flags tell snmptranslate to print OIDs numerically for output display
snmptranslate -m +F5-BIGIP-SYSTEM-MIB 1.3.6.1.4.1.3375.2.1.1.2.1.45.0
The -m flag tell snmptranslate to load that MIB in addition to the system defaults, (the leading '+' plus means "also")
snmpwalk -m +F5-BIGIP-SYSTEM-MIB -v2c -c public 10.2.50.3 .1 | grep -i memoryused
Here you can walk the entire tree and while loading the MIB to display the string values and then search
snmptranslate -m +F5-BIGIP-SYSTEM-MIB -IR -On f5
.1.3.6.1.4.1.3375
snmpwalk -m +F5-BIGIP-SYSTEM-MIB -v2c -c public 10.2.50.3 f5 | grep -i memoryused
or
snmpwalk -m +F5-BIGIP-SYSTEM-MIB -v2c -c public 10.2.50.3 .1.3.6.1.4.1.3375 | grep -i memoryused
You can also walk a subset of the tree and search for values
http://net-snmp.sourceforge.net/wiki/index.php/TUT:Using_and_loading_MIBS